1. Field of the Invention
Embodiments of the present invention find particularly advantageous but not exclusive application in the field of medical imaging, and more particularly in the field of X-ray imaging in cardiology.
2. Prior Art
X-ray imaging is now widely used for the diagnosis and processing of cardiac pathologies. The treatment may include coronaroplasty, valve replacement, electrophysiology etc.
In a certain number of interventional procedures, the practitioner must pass catheters and/or guides into vessels or cavities of the heart. These interventions enable different procedures such as embolization, dilation, desobstruction, placing of stents, and ablation. These techniques make it possible to avoid heavy surgical intervention.
During the interventional procedure, the operator guides the operating tool chiefly by means of radiography images. However, anatomical structures of strategic importance, such as the left ventricle and the pulmonary veins in the case of an interventional procedure for ablation of auricular fibrillation, and the coronary sinus and its branches in the case of biventricular stimulation procedure for example, are not depicted by X-ray systems because they show no contrast with the surrounding anatomical structures.
For all these applications, knowledge of anatomical information would be very useful during the operation to locate the tools or catheters relative to these structures.
There are many classic solutions used to make these anatomical structures visible in the radiography image. A first classic solution uses a contrast agent. This contrast agent is generally an iodized compound. However, this type of solution has drawbacks, for iodized compounds are often sources of allergies in the patient and are also toxic for the kidneys.
Another more recent approach consists of the production of a 3D image at the beginning of the operation or before the operation, using computerized tomography or magnetic resonance or by rotation of the X-ray system. This approach comprises means capable of resetting the pre-operative 3D images with projection images of the radiography system, for their subsequent fusion. This fusion enables the practitioner to view the operating tool and the anatomy at the same time. This type of approach is widely dealt with in the prior art.
However, this type of approach has drawbacks. Indeed, the main problem encountered in the specific part of the anatomy, namely the heart, is that it undergoes a high degree of motion due to the patient's heart cycle and respiration. Today, 3D computerized tomography images obtained before the operation may be synchronized with electrocardiograms, enabling the reconstruction of the heart at a specific phase of the cardiac cycle and hence the elimination of cardiac motion. Similarly, since the scanner acquisition is brief, the patient can reasonably be expected to hold his breath during the acquisition, thus eliminating the problem of respiratory motion.
Unlike pre-operation images, radiography images are dynamic and contain both heart motions and respiratory motions. Heart motion is a complex motion consisting of translation, rotation and deformation. If the registration between the pre-operation image and the X-ray image is constrained to a rigid registration, then only the radiography images acquired at the same phase of the heart cycle as the pre-operation images are used. This enables the elimination of the cardiac motion of the X-ray images. However, the respiratory motion is always present in X-ray images, and therefore does not enable precise registration with the pre-operation images.